分别在800℃、825℃、850℃焊接温度、30 m in保温时间,3 MPa焊接压力下,进行Ti-6A l-4V钛合金板与304L不锈钢网的真空扩散焊接。对接头组织结构与化学元素扩散进行了扫描电镜与能谱分析,并测试了接头的剪切强度。结果表明:不添加中间...分别在800℃、825℃、850℃焊接温度、30 m in保温时间,3 MPa焊接压力下,进行Ti-6A l-4V钛合金板与304L不锈钢网的真空扩散焊接。对接头组织结构与化学元素扩散进行了扫描电镜与能谱分析,并测试了接头的剪切强度。结果表明:不添加中间过渡层金属,可以成功地实现钛合金板与不锈钢网的扩散焊接,并使接头的剪切强度达到90 MPa以上。不锈钢网中的Fe、N、iCr扩散并固溶到钛合金中,稳定了β相,使钛合金在一定深度上,其组织由原来的α+β双相结构转变为单相的β相。不锈钢中的Cr,由于钛合金中Ti的扩散进入,而在界面发生了上坡扩散现象。这种Cr在不锈钢一定深度内的富集,形成窄长的富Cr区域,冷却后转变为硬脆的σ相。但在焊接接头中没有发现明显其它的金属间化合物或氧化物相的生成,使得接头的机械性能得到了很好的保证。展开更多
Ti-6A1-4V has a wide range of applications, especially in the aerospace field;however, it is a difficultto- cut material. In order to achieve sustainable machining of Ti?6A1-4V, multiple objectives considering not onl...Ti-6A1-4V has a wide range of applications, especially in the aerospace field;however, it is a difficultto- cut material. In order to achieve sustainable machining of Ti?6A1-4V, multiple objectives considering not only economic and technical requirements but also the environmental requirement need to be optimized simultaneously. In this work, the optimization design of process parameters such as type of inserts, feed rate, and depth of cut for Ti-6A1-4V turning under dry condition was investigated experimentally. The major performance indexes chosen to evaluate this sustainable process were radial thrust, cutting power, and coefficient of friction at the toolchip interface. Considering the nonlinearity between the various objectives, grey relational analysis (GRA) was first performed to transform these indexes into the corresponding grey relational coefficients, and then kernel principal component analysis (KPCA) was applied to extract the kernel principal components and determine the corresponding weights which showed their relative importance. Eventually, kernel grey relational grade (KGRG) was proposed as the optimization criterion to identify the optimal combination of process parameters. The results of the range analysis show that the depth of cut has the most significant effect, followed by the feed rate and type of inserts. Confirmation tests clearly show that the modified method combining GRA with KPCA outperforms the traditional GRA method with equal weights and the hybrid method based on GRA and PCA.展开更多
Hot deformation behavior and globularization mechanism of Ti-6Al-4V-0.1B alloy with lamellar microstructure were quantitatively studied through isothermal compression tests with the temperature Hot deformation behavio...Hot deformation behavior and globularization mechanism of Ti-6Al-4V-0.1B alloy with lamellar microstructure were quantitatively studied through isothermal compression tests with the temperature Hot deformation behavior and globularization mechanism of Ti-6Al-4V-0.1B alloy with lamellar microstructure were quantitatively studied through isothermal compression tests with the temperature range of 850-950 °C and strain rate range of 0.01-1.00s-1 . The results show that the peak flow stress and steady stress are sensitive to the strain rate and temperature. The value of deformation activation energy is 890.49 kJ mol-1 in (α+β) region. Dynamic recrystallization is the major deformation mechanism. Flow softening is dominated by dynamic recrystallization at 850-950 °C. TiB particles promote the recrystallization of a laths. Globularization processes consist of four steps: formation of subgrain after dynamic recovery in α plates; subgrain boundary migration caused by α/β interfacial instability; interfacial migration promoting β phase wedge into α phase; disintegrating of α laths by diffusion processes; and grainboundary sliding. Globularization mechanisms during hot deformation processes of the Ti-6Al-4V-0.1B alloy with lamellar structure are continuous dynamic recrystallization.展开更多
文摘Ti-6A1-4V has a wide range of applications, especially in the aerospace field;however, it is a difficultto- cut material. In order to achieve sustainable machining of Ti?6A1-4V, multiple objectives considering not only economic and technical requirements but also the environmental requirement need to be optimized simultaneously. In this work, the optimization design of process parameters such as type of inserts, feed rate, and depth of cut for Ti-6A1-4V turning under dry condition was investigated experimentally. The major performance indexes chosen to evaluate this sustainable process were radial thrust, cutting power, and coefficient of friction at the toolchip interface. Considering the nonlinearity between the various objectives, grey relational analysis (GRA) was first performed to transform these indexes into the corresponding grey relational coefficients, and then kernel principal component analysis (KPCA) was applied to extract the kernel principal components and determine the corresponding weights which showed their relative importance. Eventually, kernel grey relational grade (KGRG) was proposed as the optimization criterion to identify the optimal combination of process parameters. The results of the range analysis show that the depth of cut has the most significant effect, followed by the feed rate and type of inserts. Confirmation tests clearly show that the modified method combining GRA with KPCA outperforms the traditional GRA method with equal weights and the hybrid method based on GRA and PCA.
基金supported by the International Science and Technology Corporation Foundation of China(No.2012DFG51540)
文摘Hot deformation behavior and globularization mechanism of Ti-6Al-4V-0.1B alloy with lamellar microstructure were quantitatively studied through isothermal compression tests with the temperature Hot deformation behavior and globularization mechanism of Ti-6Al-4V-0.1B alloy with lamellar microstructure were quantitatively studied through isothermal compression tests with the temperature range of 850-950 °C and strain rate range of 0.01-1.00s-1 . The results show that the peak flow stress and steady stress are sensitive to the strain rate and temperature. The value of deformation activation energy is 890.49 kJ mol-1 in (α+β) region. Dynamic recrystallization is the major deformation mechanism. Flow softening is dominated by dynamic recrystallization at 850-950 °C. TiB particles promote the recrystallization of a laths. Globularization processes consist of four steps: formation of subgrain after dynamic recovery in α plates; subgrain boundary migration caused by α/β interfacial instability; interfacial migration promoting β phase wedge into α phase; disintegrating of α laths by diffusion processes; and grainboundary sliding. Globularization mechanisms during hot deformation processes of the Ti-6Al-4V-0.1B alloy with lamellar structure are continuous dynamic recrystallization.
基金Supported by the Natural Science Foundation of China (50371069)the Basic Defence Research Program of China (K1802060814)+3 种基金the Doctoral Foundation of the Educational Ministry of China (20030699013)the Aviation Science Foundation (04G53044)the Opening Foundation of Jiangxi Materials Engineering Center (ZX200301014) the Doctoral Innovation Foundation of Northwestern Polytechnical University (CX200306)
